Distributed temperature control system for point of dispense temperature control on track systems utilizing mixing of hot and cold streams

ABSTRACT

A point of dispense temperature control apparatus for a track lithography system. The apparatus includes a first liquid source characterized by a first temperature and a first flow controller coupled to the first liquid source. The apparatus also includes a second liquid source characterized by a second temperature and a second flow controller coupled to the second liquid source. The apparatus further includes a mixing element coupled to the first flow controller and the second flow controller. The mixing element is adapted to provide a mixed stream characterized by a total flow volume and a temperature intermediate to the first temperature and the second temperature. The apparatus additionally includes a sensor coupled to the mixed stream, a point of dispense heat exchanger coupled to the mixed stream, and a control loop coupled to the sensor and at least one of the first flow controller or the second flow controller. The control loop is adapted to provide a consistent total flow volume at the intermediate temperature.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 60/639,109, filed Dec. 22, 2004, entitled “Twin Architecture For Processing A Substrate,” the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of substrate processing equipment. More particularly, the present invention relates to a method and apparatus for providing point of dispense temperature control for semiconductor process chemistry. The method and apparatus can be applied to other processes for semiconductor substrates, for example those used in the formation of integrated circuits.

Modern integrated circuits contain millions of individual elements that are formed by patterning the materials, such as silicon, metal and/or dielectric layers, that make up the integrated circuit to sizes that are small fractions of a micrometer. The technique used throughout the industry for forming such patterns is photolithography. A typical photolithography process sequence generally includes depositing one or more uniform photoresist (resist) layers on the surface of a substrate, drying and curing the deposited layers, patterning the substrate by exposing the photoresist layer to electromagnetic radiation that is suitable for modifying the exposed layer and then developing the patterned photoresist layer.

It is common in the semiconductor industry for many of the steps associated with the photolithography process to be performed in a multi-chamber processing system (e.g., a cluster tool) that has the capability to sequentially process semiconductor wafers in a controlled manner. One example of a cluster tool that is used to deposit (i.e., coat) and develop a photoresist material is commonly referred to as a track lithography tool.

Track lithography tools typically include a mainframe that houses multiple chambers (which are sometimes referred to herein as stations) dedicated to performing the various tasks associated with pre- and post-lithography processing. There are typically both wet and dry processing chambers within track lithography tools. Wet chambers include coat and/or develop bowls, while dry chambers include thermal control units that house bake and/or chill plates. Track lithography tools also frequently include one or more pod/cassette mounting devices, such as an industry standard FOUP (front opening unified pod), to receive substrates from and return substrates to the clean room, multiple substrate transfer robots to transfer substrates between the various chambers/stations of the track tool and an interface that allows the tool to be operatively coupled to a lithography exposure tool in order to transfer substrates into the exposure tool and receive substrates from the exposure tool after the substrates are processed within the exposure tool.

Over the years there has been a strong push within the semiconductor industry to shrink the size of semiconductor devices. The reduced feature sizes have caused the industry's tolerance to process variability to shrink, which in turn, has resulted in semiconductor manufacturing specifications having more stringent requirements for process uniformity and repeatability. An important factor in minimizing process variability during track lithography processing sequences is to ensure that every substrate processed within the track lithography tool for a particular application has the same “wafer history.” A substrate's wafer history is generally monitored and controlled by process engineers to ensure that all of the device fabrication processing variables that may later affect a device's performance are controlled, so that all substrates in the same batch are always processed the same way.

A component of the “wafer history” is the thickness, uniformity, repeatability, and other characteristics of the photolithography chemistry, which includes, without limitation, photoresist, developer, and solvents. Generally, during photolithography processes, a substrate, for example a semiconductor wafer, is rotated on a spin chuck at predetermined speeds while liquids and gases such as solvents, photoresist (resist), developer, and the like are dispensed onto the surface of the substrate. Typically, the wafer history will depend on the process parameters associated with the photolithography process.

As an example, the thickness of the resist layer formed during a photolithography process is a function of the viscosity of photoresist and the spin rate of the spin chuck among other factors. Generally, the viscosity of the photoresist is a function of the temperature of the resist. Therefore, to achieve uniform wafer histories, it is generally desirable to control the resist temperature along with other process variables.

Depending on the particular application, the desired temperature of the resist may vary from one photoresist to another. Therefore, there is a need in the art for improved methods and apparatus that can provide temperature control for photolithography chemistry at the point of dispense.

SUMMARY OF THE INVENTION

According to the present invention techniques related to the field of substrate processing equipment are provided. More particularly, the present invention relates to a method and apparatus for providing point of dispense temperature control for semiconductor process chemistry. The method and apparatus can be applied to other processes for semiconductor substrates, for example those used in the formation of integrated circuits.

According to an embodiment of the present invention, a point of dispense temperature control apparatus for a track lithography system is provided. The apparatus includes a first liquid source characterized by a first temperature and a first flow controller coupled to the first liquid source. The apparatus also includes a second liquid source characterized by a second temperature and a second flow controller coupled to the second liquid source. The apparatus further includes a mixing element coupled to the first flow controller and the second flow controller. The mixing element is adapted to provide a mixed stream characterized by a total flow volume and a temperature intermediate to the first temperature and the second temperature. The apparatus additionally includes a sensor coupled to the mixed stream and a point of dispense heat exchanger coupled to the mixed stream. Furthermore, the apparatus includes a control loop coupled to the sensor and at least one of the first flow controller or the second-floor controller. The control loop is adapted to provide a consistent total flow volume at the intermediate temperature. In some embodiments, additional valving is provided to return one or more fluids to one or more fluid sources.

In some embodiments, the point of dispense heat exchanger is coupled to a photolithography chemical dispense system. In a specific embodiment, the control loop includes a proportional-integral-derivative controller.

According to another embodiment of the present invention, a point of dispense temperature control apparatus for a track lithography system is provided. The apparatus includes a first fluid source characterized by a first temperature and a first flow regulator coupled to the first fluid source. The apparatus also includes a second fluid source characterized by a second temperature and a second flow regulator coupled to the second fluid source. The apparatus further includes a mixing element coupled to the first fluid source and the second fluid source. The mixing element is adapted to provide a mixed stream characterized by a temperature intermediate to the first temperature and the second temperature. The apparatus additionally includes a sensor coupled to the mixed stream, a point of dispense heat exchanger coupled to the mixed stream, a fluid return path coupled to the point of dispense heat exchanger and adapted to deliver fluid to at least one of the first fluid source or the second fluid source, and a control loop coupled to the sensor and at least one of the first flow controller or the second flow controller.

In yet another embodiment according to the present invention, a method of providing distributed temperature control for multiple point of dispense heat exchangers in a track lithography system is provided. The method includes providing a first fluid stream characterized by a first temperature and providing a second fluid stream characterized by a second temperature. The method also includes providing a first fluid flow path coupled to the first fluid stream and providing a second fluid flow path coupled to the second fluid stream. The method further includes mixing the first fluid stream and the second fluid stream to provide a mixed fluid stream characterized by a third temperature, monitoring the third temperature, modulating a flow rate of at least one of the first fluid stream or the second fluid stream in response to monitoring the third temperature, and coupling the mixed stream to a plurality of point of dispense heat exchangers adapted to control a temperature associated with photolithography chemistry.

In an alternative embodiment according to the present invention, a point of dispense temperature control apparatus for a track lithography system is provided. The apparatus includes a first liquid source characterized by a first temperature coupled to a fluid line. In a particular embodiment, the first temperature is room temperature. The apparatus also includes a second liquid source characterized by a second temperature and a third liquid source characterized by a third temperature. The third temperature is less than the second temperature. The second liquid source and the third liquid source are coupled to the fluid line. The apparatus further includes a first flow controller coupled to the second liquid source and a second flow controller coupled to the third liquid source. The apparatus additionally includes a sensor coupled to the fluid line, a point of dispense heat exchanger coupled to the fluid line and a control loop coupled to the sensor and at least one of the first flow controller or the second flow controller. In some embodiments, the control loop is adapted to provide a consistent total flow volume.

In another alternative embodiment according to the present invention, a point of dispense temperature control apparatus for a track lithography system is provided. The apparatus includes a first liquid source characterized by a first temperature coupled to a fluid line. In a particular embodiment, the first temperature is room temperature. The apparatus also includes a second liquid source characterized by a second temperature and a heating element, both of which are coupled to the fluid line. The apparatus further includes a first flow controller coupled to the second liquid source. The apparatus additionally includes a sensor coupled to the fluid line, a point of dispense heat exchanger coupled to the fluid line and a control loop coupled to the sensor and at least one of the first flow controller or the heating element. In some embodiments, the control loop is adapted to provide a consistent total flow volume.

Many benefits are achieved by way of the present invention over conventional techniques. For example, embodiments of the present invention provide for packaging of temperature control hardware onboard the coat bowl, reducing tubing length between the mixer and the heat exchanger, thus reducing the distance from the temperature control hardware to the point of use. Additionally, embodiments of the present invention provide improvements in energy efficiency over other approaches, such as Peltier cooler systems. Moreover, embodiments of the present invention provide simplified temperature control systems, reducing the cost of the temperature control system in comparison with other approaches. Depending upon the embodiment, one or more of these benefits, as well as other benefits, may be achieved. These and other benefits will be described in more detail throughout the present specification and more particularly below in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of an embodiment of a track lithography tool according to an embodiment of the present invention;

FIG. 2 is a simplified schematic diagram illustrating a point of dispense temperature control system according to an embodiment of the present invention;

FIG. 3 is a simplified schematic diagram illustrating a point of dispense temperature control system according to an alternative embodiment of the present invention;

FIG. 4 is a simplified schematic diagram illustrating a multiple output temperature control system according to an embodiment of the present invention;

FIG. 5 is a simplified graph illustrating relationships between temperature set points for the mixed flow stream and flow rates according to an embodiment of the present invention;

FIG. 6 is a simplified schematic diagram illustrating another temperature control system according to an embodiment of the present invention;

FIG. 7 is a graph illustrating temperature set point change as a function of time achieved utilizing an embodiment of the present invention;

FIG. 8 is a graph illustrating temperature stability achieved utilizing an embodiment of the present invention;

FIG. 9A is a simplified schematic diagram illustrating yet another temperature control system according to an embodiment of the present invention; and

FIG. 9B is a simplified schematic diagram illustrating another alternative temperature control system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

According to the present invention techniques related to the field of substrate processing equipment are provided. More particularly, the present invention relates to a method and apparatus for providing point of dispense temperature control for semiconductor process chemistry. The method and apparatus can be applied to other processes for semiconductor substrates, for example those used in the formation of integrated circuits.

FIG. 1 is a plan view of an embodiment of a track lithography tool 100 in which the embodiments of the present invention may be used. As illustrated in FIG. 1, track lithography tool 100 contains a front end module 110 (sometimes referred to as a factory interface or FI), a central module 112, and a rear module 114 (sometimes referred to as a scanner interface). Front end module 110 generally contains one or more pod assemblies or FOUPS (e.g., items 116A-D), a front end robot 118, and front end processing racks 120A and 120B. The one or more pod assemblies 116A-D are generally adapted to accept one or more cassettes 130 that may contain one or more substrates or wafers, “W,” that are to be processed in track lithography tool 100.

Central module 112 generally contains a first central processing rack 122A, a second central processing rack 122B, and a central robot 124. Rear module 114 generally contains first and second rear processing racks 126A and 126B and a back end robot 128. Front end robot 118 is adapted to access processing modules in front end processing racks 120A, 120B; central robot 124 is adapted to access processing modules in front end processing racks 120A, 120B, first central processing rack 122A, second central processing rack 122B and/or rear processing racks 126A, 126B; and back end robot 128 is adapted to access processing modules in the rear processing racks 126A, 126B and in some cases exchange substrates with a stepper/scanner 5.

The stepper/scanner 5, which may be purchased from Canon USA, Inc. of San Jose, Calif., Nikon Precision Inc. of Belmont, Calif., or ASML US, Inc. of Tempe Ariz., is a lithographic projection apparatus used, for example, in the manufacture of integrated circuits (ICs). The scanner/stepper tool 5 exposes a photosensitive material (resist), deposited on the substrate in the cluster tool, to some form of electromagnetic radiation to generate a circuit pattern corresponding to an individual layer of the integrated circuit (IC) device to be formed on the substrate surface.

Each of the processing racks 120A, 120B; 122A, 122B and 126A, 126B contain multiple processing modules in a vertically stacked arrangement. That is, each of the processing racks may contain multiple stacked integrated thermal units 10, multiple stacked coater modules 132, multiple stacked coater/developer modules with shared dispense 134 or other modules that are adapted to perform the various processing steps required of a track photolithography tool. As examples, coater modules 132 may deposit a bottom antireflective coating (BARC); coater/developer modules 134 may be used to deposit and/or develop photoresist layers and integrated thermal units 10 may perform bake and chill operations associated with hardening BARC and/or photoresist layers.

In one embodiment, a system controller 140 is used to control all of the components and processes performed in the cluster tool 100. The controller 140 is generally adapted to communicate with the stepper/scanner 5, monitor and control aspects of the processes performed in the cluster tool 100, and is adapted to control all aspects of the complete substrate processing sequence. In some instances, controller 140 works in conjunction with other controllers, such as a post exposure bake (PEB) controller, to control certain aspects of the processing sequence. The controller 140, which is typically a microprocessor-based controller, is configured to receive inputs from a user and/or various sensors in one of the processing chambers and appropriately control the processing chamber components in accordance with the various inputs and software instructions retained in the controller's memory. The controller 140 generally contains memory and a CPU (not shown) which are utilized by the controller to retain various programs, process the programs, and execute the programs when necessary. The memory (not shown) is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits (not shown) are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like all well known in the art. A program (or computer instructions) readable by the controller 140 determines which tasks are performable in the processing chamber(s). Preferably, the program is software readable by the controller 140 and includes instructions to monitor and control the process based on defined rules and input data.

It is to be understood that embodiments of the invention are not limited to use with a track lithography tool such as that depicted in FIG. 1. Instead, embodiments of the invention may be used in any track lithography tool including the many different tool configurations described in U.S. application Ser. No. 11/112,281, entitled “Cluster Tool Architecture for Processing a Substrate” filed on Apr. 22, 2005, which is hereby incorporated by reference for all purposes and including configurations not described in the above referenced application.

During photolithography processes, the temperature of the photolithography chemistry, including both organic and inorganic resists, developers, BARCs, TARCs, and the like is controlled to achieve predetermined temperature set points. Generally, the temperature set points for coat and/or develop processes range from about 18° C. to about 28° C. In some embodiments according to the present invention, the temperature set points are maintained at a predetermined set point±0.05° C. In other embodiments, the temperature set points are maintained at a predetermined set point±0.03° C. at approximately 20° C. In yet other embodiments, the temperature set points are maintained at a predetermined set point±0.01° C. As is well known to one of skill in the art, it is desirable to control chemistry set points since the coat and develop properties, as well as the process results, are functions of temperature. As illustrated in FIG. 1, coater modules 132 and 134 generally contain multiple fluid source assemblies 260 and 262 to run different process recipes containing different materials. These materials include, but are not limited to, photoresists, developers, BARCs, TARCs, ARCs, and the like.

Accordingly, the temperature of the fluid source assemblies are each independently controlled to assure consistency in achieving desirable process results. Embodiments of the invention provide various methods and apparatus for controlling the temperature of photoresist as well as other fluids utilized in photolithography chemistries before the fluids are dispensed on the surface of a substrate during a coat and/or develop process. In some embodiments, the temperature control for develop chemistries is preferably about±0.1° C. In other embodiments, the temperature control for develop chemistries is preferably about±0.2° C.

FIG. 2 is a simplified schematic diagram illustrating a point of dispense temperature control system according to an embodiment of the present invention. A hot stream source 210 and a cold stream source 220 are provided according to embodiments of the present invention as illustrated in FIG. 2. Fluid at a temperature T_(H) is sourced from the hot stream source 210 into source line 212 and the flow rate of the fluid in line 212 is controlled using flow control valve 214. According to some embodiments, the temperature of the fluid provided by the hot stream source is a predetermined value. Merely by way of example, in some embodiments, the temperature of the hot stream source ranges from about 25° C. to about 60° C. In a specific embodiment, the temperature of the hot stream source is 30° C. Likewise, according to some embodiments, the temperature of the fluid provided by the cold stream source is a predetermined value. Merely by way of example, in some embodiments, the temperature of the cold stream source ranges from about 5 to about 25° C. In a specific embodiment, the temperature of the cold stream source is 18° C.

By way of example, embodiments of the present invention are utilized in conjunction with heat exchanging devices such as those described in commonly owned and assigned U.S. patent application Ser. No. 11/112,281, referenced above. For example, discharge nozzles containing heat exchanging devices that are adapted to heat and/or cool the nozzle body, the supply tube, and the processing fluid contained in the supply tube, for instance, photoresist, are described in the above referenced application. According to embodiments of the present invention, temperature controlled fluids are provided that are utilized in such heat exchanger applications. For example, in some embodiment, de-ionized (DI) water, de-mineralized (DM) water, DI water/ethylene glycol mixtures, DI water with anti-corrosive additives, DI water with anti-bacterial additives, combinations of these, and the like are utilized as fluids for the hot and/or cold sources. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In a particular embodiment of the present invention, source line 212 is a fluid line with a predetermined inside diameter (ID). Merely by way of example, in an embodiment, source line 212 has a ¼″ ID. In alternative embodiments, the ID of source line 212 varies with flow rate over a range from about 1/16″ to about 1″. Moreover, in some embodiments of the present invention, the flow rate of the fluid at temperature T_(H) is set at a predetermined value, such as X liters per minute (lpm). Merely by way of example, the flow rate for the hot stream is about 1 lpm in some embodiments of the present invention. In alternative embodiments, the flow rate for the hot stream ranges from about 0.1 lpm to about 3 lpm.

Cold stream source 220 provides a source of fluid at temperature T_(C) into source line 222. In a particular embodiment of the present invention, source line 222 is a fluid line with a predetermined ID. Merely by way of example, in an embodiment, source line 222 has a ¼″ ID. In alternative embodiments, the ID of source line 222 varies over a range from about 1/16″ to about 1″. In some embodiments, the hot stream source 210 and the cold stream source 220 are packaged in a single unit. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Mixer 216 is illustrated in FIG. 2 as a junction point at which the fluid in the hot stream 212 and the cold stream 222 are combined to form a mixed stream in fluid line 226. As will be evident to one of skill in the art, mixer 216 may be a “T” junction or other suitable flow combiner. As illustrated in FIG. 2, the mixed stream in fluid line 226 is at a temperature T_(M) greater than T_(C) and less than T_(H). The temperature T_(M) is a function of the flow rates of the hot and cold streams as well as the temperatures of these streams. Accordingly, a sensor 228 and controller 230 are provided according to embodiments of the present invention to achieve the desired temperature T_(M) for the mixed stream 226.

According to a particular embodiment of the present invention, a resistance temperature detector (RTD) sensor 228 is utilized to measure the temperature of the fluid flowing in the mixed stream 226. As is well known to one of skill in the art, the electrical resistivity of metals changes with temperature. Therefore, RTDs provide a resistance element for which the resistance is calibrated as a function of temperature. Embodiments of the present invention not limited to RTDs, as other temperature sensors are included within the scope of the present invention. In an embodiment, a proportional-integral-derivative (PID) controller 230 is coupled to the temperature sensor 228 and to flow control valve 224 in a feedback loop. Based on the temperature measurement provided by sensor 228, controller 230 modifies the flow rate through fluid line 222. Thus, the temperature of the mixed stream is controlled at T_(M) according to embodiments of the present invention. Embodiments of the present invention are not limited to PID controllers, as other suitable controllers are included within the scope of the present invention.

In an embodiment according to the present invention, the flow rate of the hot stream is maintained at a constant value selected to provide temperature control for chemistry through a heat exchanger at the point of dispense. As will be evident to one of skill in the art, the flow rate through the point of dispense heat exchanger will be a function of the particular heat exchanger design. Coarse adjustment of the temperature T_(M) of the mixed stream is provided in the embodiment illustrated in FIG. 2 by adjusting the temperature set point T_(H) of the hot stream. In an alternative embodiment, coarse adjustment of the temperature T_(M) is provided by adjusting the flow rate of the hot stream or combinations of the temperature and flow rate. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. Fine adjustment of the temperature of the mixed stream is provided by the feedback loop including the controller 230, thereby varying the flow rate of the cold stream.

Flow control valve 240 is utilized to control the flow rate of fluid to point of dispense heat exchanger 242 and the return to the hot stream source 210. In a particular embodiment according to the present invention, flow control valve 240 is adjusted to provide a flow rate to the point of dispense heat exchanger substantially equal to the flow rate in fluid line 212, namely X lpm. Accordingly, the flows sourced by and returned to the hot stream source 210 are equal. In some embodiments, substantially equal flow rates include flow rates in which the flow rate in fluid line 212 is within 90% of the flow rate in the return line to the hot stream source. In other embodiments, substantially equal flow rates include flow rates in which the flow rate in fluid line 212 is within 95%, 97% or 99% of the flow rate in the return line to the hot stream source. Fluid from the mixed stream not returned to the hot stream source is returned to the cold stream source through fluid line 244. In some embodiments, an additional flow control valve 246 is utilized to control the flow of fluid in cold stream return line 244.

Although FIG. 2 illustrates the use of flow control valves to regulate the flow in lines 212, 222, and the hot and cold return lines, this is not required by the present invention. In alternative embodiments, other flow control mechanisms are utilized including pressure regulators that pressure balance lines 212 and 222. Merely by way of example, flow restrictors including valves, orifices, and the like are utilized according to embodiments of the present invention. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

According to embodiments of the present invention, the point of dispense heat exchanger 242 is coupled to fluid lines associated with the photolithography chemistry. As an example, the point of dispense heat exchanger is coupled to a photoresist line in a particular embodiment. By providing a heat exchanger at the point of dispense, variations in chemistry temperatures as the various fluids travel through delivery paths are minimized. Therefore, the temperature of the photoresist, solvents, developers, and the like is controlled to achieve desired process control, uniformity, and repeatability.

FIG. 3 is a simplified schematic diagram illustrating a point of dispense temperature control system according to an alternative embodiment of the present invention. Hot stream source 310 and cold stream source 330 are provided as illustrated in FIG. 3. As illustrated in FIG. 3, hot stream source 310 and cold stream source 330 are combined in a single unit 305. Fluid at temperature T_(H) is sourced from the hot stream source 310 in a manner similar to that as illustrated in FIG. 2. Pressure regulator 312 is utilized to control the flow through fluid line 314. In some embodiments, pressure regulator 312 is replaced by a variable rate flow control valve.

Flow monitor 316 is coupled to the fluid line 314 to monitor the flow rate through the line. In an embodiment according to the present invention, a rotameter available from Omega Engineering, Inc. of Stamford, Conn. is utilized for this flow monitoring function. In some embodiments, the flow rate through line 314 is a predetermined amount of about 1 lpm. In alternative embodiments, the flow rate ranges from about 0.1 lpm to about 3 lpm. Monitoring RTD 318 along with a check valve (not shown) is coupled to the line 314 downstream of the flow monitor 316. As will be evident to one of skill in the art, the use of a check valve prevents back stream flow in line 314.

Cold stream source 330 provides a source of fluid at temperature T_(C) into source line 332. Dome regulator 348, needle valve 334, RTD 336, and a check valve(not shown) are coupled to cold stream line 332 as illustrated in FIG. 3. The hot stream and the cold stream are mixed at the junction of the hot and cold streams and mixed in a mixer 340. As illustrated in FIG. 3, a mixed stream flows in the fluid line downstream of the mixer at a temperature T_(M) greater than T_(C) and less than T_(H). The intermediate temperature T_(M) is a function of the flow rates of the hot and cold streams as well as the temperatures of the streams.

As illustrated in FIG. 3, in some embodiments of the present invention, a temperature sensor, such as an RTD sensor 342, is utilized to measure the temperature of the fluid flowing in the mixed stream. Embodiments of the present invention not limited to RTDs, as other temperature sensors are included within the scope of the present invention. As further illustrated in FIG. 3, a controller 344 and a signal converter 346 are coupled to the sensor 342 and the dome regulator 348 in a feedback loop. In an embodiment, a PID controller 344 is utilized to provide feedback and control signals for the temperature control system. Moreover, an electro-pneumatic regulator, such as an ITV regulator 346 available from SMC Corporation of America of Indianapolis, Ind., which controls air pressure in proportion to an electrical signal is illustrated in FIG. 3. Thus, electrical signals provided by the controller 344 are converted to pneumatic signals by the converter 346. The pneumatic signals are utilized in turn to regulate the flow of the cold stream through dome regulator 348. Therefore, based on the temperature measurement provided by sensor 342, controller 344 and signal converter 346 modify the flow rate through fluid line 332.

In the embodiment according to the present invention illustrated in FIG. 3, the flow rate of the hot stream is monitored and regulated prior to mixing with the cold stream. Feedback from the mixed stream line is utilized to regulate the flow in the cold stream line, thereby controlling the temperature of the mixed stream. The point of dispense heat exchanger is utilized to regulate the temperature of various photolithography chemistry fluids as described above. Generally, coarse adjustment of the temperature T_(M) of the mixed stream is provided by adjusting the temperature set point T_(H), the flow rate of the hot stream, and/or combinations thereof. Fine adjustment of the temperature of the mixed stream is provided by the feedback loop regulating the flow rate in the cold stream line. After passing through the point of dispense heat exchanger 350, the mixed stream returns to the source unit 305 through the illustrated fluid lines. Variable rate flow control valves 352 and 354 are utilized in the embodiment illustrated in FIG. 3 to control the flow rates of the mixed stream in the return paths to the fluid source.

As will be evident, in alternative embodiments the flow rate of the hot stream is monitored and regulated by a feedback loop. In this alternative embodiment, fine adjustment of the temperature of the mixed stream is provided by the feedback loop regulating the flow rate in the hot stream. In yet other alternative embodiments, a control loop coupled to both the cold stream flow regulator and the hot stream flow regulator is utilized. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

According to some embodiments of the present invention, the total flow in the mixed stream is regulated through the use of the variable flow control valves illustrated in FIG. 3 to maintain a consistent total flow through the point of dispense heat exchanger. Provision of a consistent total flow rate is accomplished in a specific embodiment by referencing the temperature and flow rate of the hot stream and adjusting the cold stream flow in response to these measurements. In another specific embodiment, the temperature and flow rate of the cold stream are referenced. In other embodiments, the hot and cold streams are pressure balanced to provide a consistent total flow rate. In embodiments of the present invention, a consistent or constant flow rate is provided for a predetermined time, for example, during a series of dispense operations. A constant flow rate is defined in some embodiments by a flow rate varying less than 10% during the predetermined period. In other embodiments, a constant flow rate is defined by a variation of less than 5%, less than 3%, or less than 1%.

FIG. 4 is a simplified schematic diagram illustrating a multiple output temperature control system according to an embodiment of the present invention. As illustrated in FIG. 4, hot stream source 410 and cold stream source 420 are coupled to a number of distributed point of dispense heat exchangers (PDHX) PDHX 1 through PDHX n. Accordingly, multiple branches are provided utilizing common system components, reducing system costs and complexity while providing independently controlled point of dispense heat exchangers adapted to provide different temperature set points. The point of dispense temperature control systems illustrated in FIGS. 2 and 3, as well as other configurations, are thereby operated in parallel as illustrated in FIG. 4. Accordingly, embodiments of the present invention provide for multiple independent point of dispense temperature control systems operating at predetermined temperatures.

In some embodiments of the present invention, a first number of chemical delivery nozzles are provided in a second number of groupings, each of the first number of chemical delivery nozzles coupled to a point of dispense heat exchanger. In a specific embodiment, four groups of three nozzles are provided for dispense of resist and other coating liquids. Each of the groups of nozzles is coupled to a point of dispense heat exchanger operated at a set point temperature. Thus, three nozzles are maintained at a first temperature, three other nozzles are maintained at a second temperature, etc. Utilizing the embodiments of the present invention illustrated in FIGS. 2 and 3, the first temperature may be maintained at a different temperature than the second temperature.

FIG. 5 is a simplified graph illustrating relationships between temperature set points for the mixed flow stream and flow rates according to an embodiment of the present invention. In FIG. 5, the flow rate of the hot and cold flows measured in liters per minute (lpm) is plotted on the left y-axis and the set point temperatures of the hot and cold flows in degrees Centigrade are plotted on the right y-axis. Thus, as illustrated in FIG. 5, the hot flow set point is set at 30° C. and the cold flow set point is set at 16° C. For these predetermined set points, the flow rate of the hot and cold flows can be determined as a function of the final temperature set point for the mixed stream in degrees Centigrade, which is plotted along the lower x-axis, titled “Mixed Flow Set Point.”

As an example, to obtain a final temperature set point for the mixed stream of 21° C., a flow rate of about 0.7 lpm for the hot flow (reference A on the left y-axis of FIG. 5) and a flow rate of about 1.3 lpm for the cold flow (reference B) are utilized. At the intersection of the hot and cold flow rates, a temperature of 23° C. (equal to the average of 16 and 30) is obtained for equal hot and cold flow rates of 1.0 lpm. This set point is illustrated by dashed line C in FIG. 5. As will be evident to one of skill in the art, similar charts may be produced as a function of the hot and cold flow set points and flow rates.

FIG. 6 is a simplified schematic diagram illustrating another temperature control system according to an embodiment of the present invention. As illustrated in FIG. 6, a first flow controller 610 is coupled to a hot water line 616. Under control of RTD 622, and control loop 630, the first flow controller 610 is operable to modulate the flow of fluid in hot water line 616. A second flow controller 612 is coupled to a cold water line 614. In the embodiment illustrated in FIG. 6, the second flow controller 612 is maintained at a constant flow rate set point. As described below, set points of 1.0, 1.5, and 2.0 lpm, providing a constant flow rate in cold water line 614, are provided in some embodiments. As will be evident to one of skill in the art, the selection of the cold water line 614 as the constant flow source is not required according to embodiments of the present invention. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Hot water line 616 and cold water line 614 are joined prior to their combined flow entering static mixer 620. An RTD 622 is coupled to the output of a first static mixer 620. The output of the RTD 622 is fed back to flow controller 610 via control loop 630. After passing through RTD 622, the combined flow passes through a second static mixer 624. RTD 626 is coupled to the output of the second static mixer 624. The output of RTD 626 is provided to a data acquisition system (not shown) for data collection and analysis.

FIG. 7 is a graph illustrating temperature set point change as a function of time achieved utilizing an embodiment of the present invention. As illustrated in FIG. 7, the apparatus illustrated in FIG. 6 is utilized to generate a series of temperature set points. The data presented in FIG. 7 was collected at the second RTD 622 as illustrated in FIG. 6. In the embodiment illustrated in FIG. 7, set points at 20° C., 22° C., 24° C., 26° C., 28° C., and 30° C. are demonstrated as a function of time. Referring to FIG. 7, each of the set points listed above are maintained for a time period of approximately 20 seconds. Temperature set points are demonstrated in the figure for a single flow rate for the cold stream of 1.0 lpm, although other flow rates (e.g. 1.5 lpm and 2.0 lpm) are included in alternative embodiments of the present invention.

As illustrated in FIG. 7, embodiments of the present invention provide for controllable and stable set points for point of dispense heat exchangers. Embodiments of the present invention are thus useful to regulate the temperature of photolithography chemicals, such as resist. As will be evident to one of skill in the art, the regulation of these temperatures will provide for uniform wafer histories and repeatable coating and dispense operations.

FIG. 8 is a graph illustrating temperature stability achieved utilizing an embodiment of the present invention. In FIG. 8, the temperature of the mixed stream measured at RTD 626 is plotted as a function of time. For reference, boundaries associated with±3σ, calculated based on data collected using the system illustrated in FIG. 6, are illustrated in FIG. 8 at about 19.99° C. and 20.05° C. The flow rate of the cold stream was set at 1.0 lpm during the collection of the data illustrated in FIG. 8. The temperature of the mixed stream varies from about 20.03° C. to about 20.00° C., exhibiting a variation of about 0.03° C. at a set point temperature of about 20° C., well within the±3σ variation limits.

FIG. 9A is a simplified schematic diagram illustrating yet another temperature control system according to an embodiment of the present invention. A source of fluid 910, water in some embodiments, is provided at a predetermined temperature. Generally, the predetermined temperature is room temperature, e.g., 20° C.-25° C. For purposes of clarity flow and pressure control apparatus associated with the room temperature source 910 are not illustrated in FIG. 9A. In alternative embodiments, the temperature of source 910 is selected to provide a temperature approximately equal to the average dispense temperature of the photolithography chemicals, thus reducing operating costs.

A source of hot fluid 912 and a source of cold fluid 914 are provided and connected to the output of the room temperature source 910. As illustrated in FIG. 9A, flow control valves 916 and 918 are utilized to modulate the flow of fluids from the hot source and the cold source, respectively. Controlled amounts of the hot and cold fluids are delivered to the fluid line coupled to temperature sensor 920. In some embodiments, the temperature sensor is an RTD or other suitable sensor. A control system, not shown, utilizes measurements of the fluid temperature at the temperature sensor 920 to control the flow through valves 916 and 918, providing the desired temperature fluid to the point of dispense heat exchanger 922.

In some embodiments of the present invention utilizing the temperature control system illustrated in FIG. 9A, a fluid return path is provided for the fluid passing through the point of dispense heat exchanger 922. In alternative embodiments, the temperature control system does not recycle the temperature control fluid, but utilizes a single pass system. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 9B is a simplified schematic diagram illustrating another alternative temperature control system according to an embodiment of the present invention. A source of fluid 950, water in some embodiments, is provided at a predetermined temperature. Generally, the predetermined temperature is room temperature, e.g., 20° C.-25° C. In alternative embodiments, the temperature of source 950 is selected to provide a temperature approximately equal to the average dispense temperature of the photolithography chemicals, thus reducing operating costs.

A source of cold fluid 952 is provided and connected to the output of the room temperature source 950. As illustrated in FIG. 9B, flow control valve 954 is utilized to modulate the flow of fluid from the cold source. Controlled amounts of the cold fluid is delivered to the fluid line coupled to the room temperature source. Additionally, a heating element 956 is coupled to the mixed stream formed by the room temperature source 950 and cold source 952. In some embodiments, the heating element 956 is a resistive heater adapted to raise the temperature of the fluid passing through line 958 by approximately 2-5° C. A control system, not shown, utilizes measurements of the fluid temperature at the temperature sensor 960 to control the flow through valve 954 and/or the operation of heating element 956, thereby providing the desired temperature fluid to a point of dispense heat exchanger (not shown). The cold source is positioned after the heating element in alternative embodiments.

In some embodiments of the present invention utilizing the temperature control system illustrated in FIG. 9B, a fluid return path is provided for the fluid passing through the point of dispense heat exchanger connected to fluid line 958. In alternative embodiments, the temperature control system does not recycle the temperature control fluid, but utilizes a single pass system. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

While the present invention has been described with respect to particular embodiments and specific examples thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention. The scope of the invention should, therefore, be determined with reference to the appended claims along with their full scope of equivalents. 

1. A point of dispense temperature control apparatus for a track lithography system, the apparatus comprising: a first liquid source characterized by a first temperature; a first flow controller coupled to the first liquid source; a second liquid source characterized by a second temperature; a second flow controller coupled to the second liquid source; a mixing element coupled to the first flow controller and the second flow controller, the mixing element being adapted to provide a mixed stream characterized by a total flow volume and a temperature intermediate to the first temperature and the second temperature; a sensor coupled to the mixed stream; a point of dispense heat exchanger coupled to the mixed stream; and a control loop coupled to the sensor and at least one of the first flow controller or the second flow controller, wherein the control loop is adapted to provide a consistent total flow volume at the intermediate temperature.
 2. The apparatus of claim 1 wherein the first liquid source and the second liquid source are packaged in a single unit.
 3. The apparatus of claim 1 wherein the control loop is coupled to the sensor and the first flow controller.
 4. The apparatus of claim 1 wherein the control loop is coupled to the sensor and the second flow controller.
 5. The apparatus of claim 1 further comprising: a third flow controller coupled to the mixed stream and the first liquid source; and a fourth flow controller coupled to the mixed stream and the second liquid source.
 6. The apparatus of claim 5 wherein a flow rate of the first fluid through the first flow controller is substantially equal to a flow rate of the mixed stream through the third flow controller.
 7. The apparatus of claim 1 wherein the sensor is a resistance temperature detector sensor.
 8. The apparatus of claim 1 wherein the control loop comprises a proportional-integral-derivative controller.
 9. The apparatus of claim 8 wherein the proportional-integral-derivative controller provides a control signal utilized to modulate the flow rate of the second fluid through the second flow controller.
 10. The apparatus of claim 1 wherein the first flow controller and the second flow controller are adapted to pressure balance a first fluid pressure associated with the first liquid source and a second fluid pressure associated with the second liquid source.
 11. The apparatus of claim 1 wherein the point of dispense heat exchanger is coupled to a photolithography chemical dispense system.
 12. A point of dispense temperature control apparatus for a track lithography system, the apparatus comprising: a first fluid source characterized by a first temperature; a first flow regulator coupled to the first fluid source; a second fluid source characterized by a second temperature; a second flow regulator coupled to the second fluid source; a mixing element coupled to the first fluid source and the second fluid source, the mixing element being adapted to provide a mixed stream characterized by a temperature intermediate to the first temperature and the second temperature; a sensor coupled to the mixed stream; a point of dispense heat exchanger coupled to the mixed stream; a fluid return path coupled to the point of dispense heat exchanger and adapted to deliver fluid to at least one of the first fluid source or the second fluid source; and a control loop coupled to the sensor and at least one of the first flow controller or the second flow controller.
 13. The apparatus of claim 12 wherein the flow rate of the mixed stream is characterized by a constant total flow rate during a predetermined time period.
 14. The apparatus of claim 12 wherein the sensor is a resistance temperature detector sensor.
 15. The apparatus of claim 12 wherein the control loop comprises a proportional-integral-derivative controller and an electro-pneumatic regulator.
 16. The apparatus of claim 15 wherein the proportional-integral-derivative controller provides a control signal utilized to modulate the flow rate of the second fluid through the second flow controller.
 17. A method of providing distributed temperature control for multiple point of dispense heat exchangers in a track lithography system, the method comprising: providing a first fluid stream characterized by a first temperature; providing a second fluid stream characterized by a second temperature; providing a first fluid flow path coupled to the first fluid stream; providing a second fluid flow path coupled to the second fluid stream; mixing the first fluid stream and the second fluid stream to provide a mixed fluid stream characterized by a third temperature; monitoring the third temperature; modulating a flow rate of at least one of the first fluid stream or the second fluid stream in response to monitoring the third temperature; and coupling the mixed stream to a plurality of point of dispense heat exchangers adapted to control a temperature associated with photolithography chemistry.
 18. The method of claim 17 wherein the third temperature is intermediate to the first temperature and the second temperature.
 19. The method of claim 17 wherein each of the plurality or point of dispense heat exchangers are coupled to a portion of a photolithography chemistry dispense system.
 20. The method of claim 19 wherein the portions of the photolithography chemistry dispense system are operable to provide independent temperature set points for photolithography chemistry fluids. 